to pull up, to eradicate
揠 centers on forcefully pulling something out from where it is fixed: pulling up plants by the roots or eradicating something completely.
揠 combines 扌 (hand) with 匽, which likely contributes the sound and may relate to hiding or stopping, but the exact historical development is uncertain.
The hand radical 扌 beside 匽 suggests a hand pulling something out from a hidden or stuck place, like yanking a weed up by the roots.
For サツ, imagine pulling up weeds with a sharp, sudden motion that makes a 'satsu' sound as they come out of the ground.